How much power do you need a circulation pump for heating. Features of the selection of a circulation pump for a heating system
1. Starting point when choosing circulation pump for the heating system is the heat demand of the building, calculated for the coldest season.
In professional design, this indicator is determined on a computer. Approximately it can be calculated by the area of the heated room.
According to European standards, heating 1 sq.m in a house with 1-2 apartments requires 100 W, and for apartment buildings 70 W. If the condition of the building does not meet the standards, the designer takes into account the higher specific heat consumption.
For residential buildings with improved thermal insulation and industrial premises, 30–50 W / sq.m.
- - for 1-2-storey buildings– 173 W/sq.m at design outdoor air temperature of -25°C and 177 W/sq.m at -30°C;
- for 3-4-storey buildings- respectively 97 and 101 W / sq.m.
Using the interpolation method, we obtain that in Khabarovsk the specific heat demand of 1-2-storey residential buildings is 177.8 W/sq.m, and 3-4-storey buildings - 101.8 W/sq.m.
2. Having determined the heat consumption (G, W), you should proceed to the calculation of the required pump performance (delivery) using the formula:
Q = G / 1.16 x DT (kg / h), where:
- DT- the temperature difference in the supply and return pipeline heating schemes (in standard two-pipe systems it is 20 degrees C; in low-temperature systems 10 degrees C; for warm floors 5 degrees C);
1,16 - specific heat capacity of water (W * h / kg * deg C). If another coolant is used, appropriate adjustments must be made to the formula.
This calculation method is offered by foreign designers. The mandatory annex to SNiP 2.04.05-91* contains the following formula:
Q = 3.6 x G/(c x DT) (kg/h) where:
- c- specific heat capacity of water, equal to 4.2 kJ / kg * deg C.
3. In addition to the necessary flow, the pump must provide pressure (pressure) sufficient to overcome the resistance of the pipeline network. For right choice you need to determine the losses in the longest line of the circuit (to the farthest radiator).
When designing new system accurate calculations are possible, taking into account the resistance of all elements of the thread (pipes, fittings, fittings and devices). Usually the necessary information is given in the passports for the equipment.
Here you can use the formula:
H \u003d (R x l + * Z) / p x g (m), where:
- R– resistance in a straight pipe (Pa/m);
l– pipeline length (m);
*Z– resistance of fittings, etc. (Pa);
p- density of the pumped medium (kg / m3);
g- free fall acceleration (m/sq.s).
Empirically obtained data indicate that the resistance of straight pipe sections (R) is of the order of 100–150 Pa/m. This corresponds to the required pump head of 0.01–0.015 m per 1 m of pipeline. In the calculations, you need to take into account the length of both the supply and return lines.
It has also been experimentally determined that about 30% of the losses in a straight pipe are lost in fittings and fittings. If the system has a thermostatic expansion valve, about 70% more is added.
A three-way mixer in the control unit of the entire heating system or a device that prevents natural circulation accounts for 20%.
Wilo specialists E. Buscher and K. Walter recommend the following formula for an approximate calculation of the head (in meters):
H = R x l x ZF, where
- ZF- safety factor.
If the installation is not equipped with either a thermostatic expansion valve or a mixer, ZF = 1.3; for a circuit with a thermostatic expansion valve ZF = 1.3 x 1.7 = 2.2; when the system includes both devices ZF = 1.3 x 1.7 x 1.2 = 2.6. According to a simplified method, 2.2 for heating systems, 2.6 for hot water supply can be considered.
Finally
Having determined the so-called operating point of the “circulator” (pressure and flow), it remains to select a pump with a similar characteristic in the catalogs. In terms of performance (Q), the operating point should fall in the middle third of the diagram (Fig. 1).
How to choose a circulator for a heating system
We must not forget that the calculated parameters are necessary for the operation of the system when maximum load. Such conditions are extremely rare, most heating season the need for heat is not so great.
Therefore, if in doubt, a smaller pump should always be selected. This allows not only to save on its purchase, but also to reduce further energy costs.
An example as a test
The correctness of the calculations according to the presented method can be verified by comparing their results with the results of exact calculations in a real project, performed in accordance with SNiP.
It was preliminary determined that the building's demand for heat is 45.6 kW, the coolant consumption required for heating is 2.02 cubic meters per hour. The piping scheme to the most distant radiator includes four sections and a heat control valve.
The total pressure loss in them is equal to:
DP = 0.63 + 0.111 + 0.142 + 0.289 = 1.178 m
According to SNiP 2.04.05-91*, 10% should be added to this value for unaccounted for pressure losses:
DP = 1.178 x 1.1 = 1.296 m
Thus, the “circulator” for this system must provide a supply of 2.02 cubic meters per hour of coolant and a head of 1.3 m.
When calculating according to the method described in the article, we get:
H \u003d 0.015 x (3.2 + 4.4 + 8.9 + 21.7) x 1.3 x 1.7 \u003d 1.266 m,
which is not too different from the value obtained earlier.
Water heating with the presence of a special pump necessary for pumping the coolant is in many ways superior to similar systems with natural circulation of the working medium. Efficiency with the installation of such a device increases significantly. In addition, there are additional features in terms of adjustment. With regard to the pipelines used, it is possible to choose products with a smaller diameter, and this allows you to create very economical heating networks.
The forced circulation heating system will work properly, provided that the performance and some other pump parameters are correctly selected. First of all, it should be clarified how much coolant the product can pump over a specific period of time.
Initially purchase a pump model with a large margin performance characteristics impractical. Firstly, the cost of the device will be too high, so you will have to spend a significant part of the budget. Secondly, the device will consume excess energy, since with an increase in power, its consumption also increases.
Last but not least, the choice should take into account the factors of comfort and quality characteristics. For a quiet stay, it is better, of course, to purchase a device that does not create much noise and is durable. Such requirements are usually met by products of trusted manufacturers that have been on the market for a long time.
Calculator for calculating the performance of the circulation pump
Instrument Performance Calculation
Calculate the throughput of the pump for a certain time will help the calculator, which has only two fields for entering information. The peculiarity of the computational process lies in the fact that it is not ordinary water that is pumped, but a carrier of thermal energy. From the boiler working fluid distributed through pipelines.
The simplified formula for calculations is as follows:
G = W/(∆t x Kt) , where
G – throughput in kilograms per hour;
W – power of the boiler used for heating system;
∆t - the temperature difference between the supply and return pipelines (taken thermal energy heaters);
Kt - coefficient denoting the thermal capacity of the working fluid.
The power of the heating boiler must be known. If the system is arranged from scratch, then this parameter is calculated using a special formula. For the temperature difference, you can take the average value. For water-type underfloor heating circuits, it is 5 degrees, for heating radiators - 20 degrees, and for - 15 degrees. The coefficient indicated in the formula can be taken as 1.16.
In order to mount a water heating system with forced circulation, it is necessary to correctly select and install a circulation pump in it, which will provide it. Currently, there is a wide variety of models of different designs and with different characteristics. Which one and how to choose? In this article, we will look at how to select a circulation pump for a heating system on our own.
In order to select a circulation pump for a heating system, it is necessary to determine its main characteristics that will be required during its operation: the working head (pressure) and the flow (flow) that it must provide. And in order to determine them, it is necessary to know both the power of the heating system itself and its hydraulic resistance. Both of these indicators can be calculated more accurately, using complex calculations, or simplified, using a calculation that almost anyone can do. We will consider it.
Heating system power and required flow
As we have already said, when selecting a circulation pump for a heating system, first of all, it is required to determine its thermal power. It must correspond to the amount of heat required to heat the building, which, in turn, is determined by its area and the level of thermal insulation of external structures (walls, floors, ceilings, windows, doors). To calculate this indicator accurately, it is necessary to take into account their thickness, material, design and other factors.
In order to simplify the calculation, you can take an average of 100-150 W of thermal energy for every 1 m 2 of a room, with a ceiling height of up to 3 m. If the building is insulated well enough, you can take a lower value. So, for example, a well-insulated house with an area of 100 m 2 will require heating with a thermal power of 10 kW. If the circulation pump is installed in an existing system with natural circulation, then its power can be found from technical specifications boiler that is installed.
Now, knowing the required heating power, you can determine the required performance (flow) of the circulation pump using one of the following formulas:
P \u003d Q / (1.16 x ΔT),(kg/h)
- Q – thermal power heating systems (W);
- ∆T- the temperature difference between the supply and return pipes (for two-pipe systems it is usually taken within 20 ° C, and for a warm floor - about 5 ° C);
- 1,16 is the coefficient of specific heat capacity of water, Tue× h/kg× °С(for other types of coolants, this indicator will be somewhat different and can be found in reference literature or on the Internet).
Another formula by which you can calculate the required performance:
P \u003d 3.6 x Q / (c × ΔT),(kg/h)
where: With– specific heat capacity of the coolant (for water is 4,2 kJ/kg×°С).
For example, for the heat power of 10 kW discussed above and two-pipe system water heating according to the first formula we get:
P \u003d 10000 / (1.16 × 20) \u003d 431 kg / h or 0.43 m3/h(for heat carrier-water 1kg=1l).
Hydraulic resistance and required head
In order to make the selection of a pump for a heating system according to this parameter, it is necessary to calculate the hydraulic resistance that it will need to overcome in order to ensure the normal circulation of the coolant (water). You can use the following formula to calculate:
J = (F+R× L)/p× g(m)
- L– length of the system to the most distant radiator (m);
- R- hydraulic resistance of the straight section of the pipe (Pa / m);
- p- heat carrier density (for water - 1000 kg / m 3);
- F is the resistance of the connecting and stop valves(Pa);
- g– 9.8 m/s2 (gravitational acceleration).
For accurate calculation values R and F can be found in the reference literature. For a simplified one, you can take the averaged data obtained experimentally:
R— within 100-150 Pa/m;
F- depending on the type:
- in each connecting fitting, an additional 30% is lost to the losses in the straight pipe in this section;
- in a three-way mixer or similar devices - additionally up to 20%;
- in thermostats - up to 70% of the losses in a straight pipe.
In addition to the above, you can use another formula proposed by experts from the well-known German company Wilo:
J=R× L × k, m
where: k- coefficient taking into account the resistance in shut-off and control valves and which has the following values:
- 1.3 - for simple systems without complex fittings;
- 2.2 - with control valves;
- 2.6 - for more complex ones.
If one pump will circulate in a heating system with several circuits (branches), then for its selection it is necessary to take into account their total resistance. If it is planned to install a separate pump for each circuit, then each such branch of the main must be calculated separately, both in terms of thermal power and in terms of hydraulic resistance. At the same time, the number of storeys of the building, when calculating the pressure, does not play a big role. Since in a closed system the liquid columns of the supply and return lines are balanced.
How to choose a circulation pump according to the data received
Having now calculated and knowing the main required parameters of the characteristics of the circulation pump, you can easily select the required option using the performance graphs that are in the instruction manual or passport of any model. As a rule, such graphs have two axes: head (pressure) and flow (flow).
Rice. 1 Example of a circulation pump curve
We can plot the results obtained earlier on the existing chart, plotting their values along the corresponding axes, and at their intersection get a working point, which should be slightly below the line AT graph showing the characteristics of a given pump (the best option is A2). If the point is above ( A3) - such a pump is not suitable, it will not be able to provide the necessary circulation. If the operating point is significantly below the graph ( A1), this is also not very good, since it will provide circulation, but having too much supply, it will consume more electricity, and its cost will also be higher than a pump with more modest characteristics.
Rice. 2 Selection of the pump according to the graph of its characteristics
If the model has not one, but 2 or 3 speeds, then there will be 2 or 3 lines on the performance graph, respectively. In this case, it is necessary to select a pump for the heating system according to the schedule of the speed at which it is supposed to operate.
Other factors influencing the choice
The selection of a circulation pump for a heating system, in addition to those discussed above, its main characteristics are also influenced by other factors, such as: reliability, workmanship, temperature regime operation, cost, method of connection, etc.
Workmanship, reliability, and durability tend to be directly related to cost. Manufacturers that offer reliable and high-quality models, such as Grundfos (Denmark), Wilo (Germany), DAB, Lowara, Ebara and Pedrollo (Italy), evaluate their products accordingly.
wilo circulation pump in a heating system
Domestic or Chinese models are cheaper, but the guarantee of their quality, respectively, is lower. Here, everyone must make a choice himself, choose a quality product at a higher price or buy a cheaper circulation pump, with the knowledge that it may soon have to be changed.
If you want to save money, you can also buy used Grundfos or Wilo, they can often work normally longer than new Chinese ones, but it’s better to buy them from familiar, trusted specialists who give a certain guarantee.
In addition, when choosing, it is necessary to pay attention to the type and diameter of the connection between the pump and the pipes of the system. Some models are equipped with connecting elements such as "American", and some will have to be selected independently.
Another parameter that you need to pay attention to is the temperature regime for the operation of the circulation pump, which should be in the passport. This is especially important if it will be installed on the supply pipe in a system with solid fuel boiler. In this case, the maximum allowable temperature must be at least 110°C. If, however, the pump will be installed on the "return", then this is not so important, since the temperature at the boiler inlet rarely exceeds 80 ° C.
Related videos
How to choose a pump for heating?
Often, "classical" heating systems based on natural circulation coolant, there is not enough coolant in the system, because. pressure in such systems does not exceed 0.6 MPa. To increase the pressure and improve the circulation of the coolant, it is necessary to install a circulation pump.
The main task of the work circulation pump- help the coolant overcome the resistance that occurs in certain sections of the heating system. The principle of operation of such a pump is simple, the pump sucks in the coolant from one side and, due to centrifugal force, pumps it into the pipeline on the other, which arises from the rotation of the impeller, as a result of which a vacuum occurs in the inlet pipe, and compression occurs at the outlet.
Circulation pumps are divided into two types: with a "dry" rotor and with a "wet" one. In the design with a "dry" rotor, the rotor does not come into contact with the coolant, its working part is separated from the electric motor by sealing rings. Such pumps have a high efficiency (80%), but, unfortunately, they emit a loud noise during operation. In wet rotor pumps, the impeller is immersed in the coolant along with the rotor. The coolant in this case acts as a lubricant and cools the engine. Much less noisy, do not require maintenance for years, but have a lower efficiency (50%). It is because of this that "wet" type pumps are mostly used for circulation in domestic heating systems.
How to choose a circulation pump?
To select a pump, you need to know several parameters. 1. Pump connection diameter. 2. The volume of the pumped coolant (pump performance). 3. Lifting height of the system (maximum head). 4. Manufacturer.
Therefore, if you decide to buy a circulation pump, be sure to consult with the person who will install it or with the specialists of our store + 7 499 272-2229
How to choose on our website
If you have all the parameters of the required pump, go to the circulation pumps section. Open the feature filter, enter the required parameters, for convenience, each product card has a "Compare" button
Remember that pumps are mass-produced with average parameters, and each heating system is individual. Excessive power will cause noise in the pipes during operation. The right decision would be to choose a pump with several operating modes, the power of which exceeds the calculated one by 5-10%.
Be sure to check out our special offers for circulation pumps!Heating systems in which the coolant moves through pipes due to natural circulation are gradually becoming a thing of the past. This is due to the emergence of new materials for the manufacture of pipes and the low efficiency of the heating system itself. For efficiency increase systems, special units are used - pumps, which can now be seen in many private houses and even apartments in multi-storey buildings. About how to choose the right type of equipment for the heating network, we will tell in this article!
How to choose a circulation pump for a heating system?
To improve the heating efficiency, a pump is often introduced into the heating system, causing forced circulation of the coolant. Due to the use of this unit, not only efficiency increases, but also fuel costs decrease. The selection of a suitable model must be taken responsibly, and it is better to entrust the choice to professionals. Do you want to do everything yourself? Then to make the right decision you need to know:
- The exact area of the heated room.
- The height of the location point of the uppermost element of the heating system in relation to the pump.
- Approximate resistance of the existing heating network.
Let's start our calculation by determining the resistance, for this we find out the conditional passage of the system with various types of heating devices. FROM cast iron radiators DN 40 system resistance is 1 m. With aluminum batteries DN 32 - 1.2-1.5 m. With bimetallic products DN 25 - 2 m.
Now we need the distance from the pump to the top heater. Let's say that it is 4 m, while the heating system uses modern bimetal radiators. Therefore, to find out the pressure that the pump should give, we need to add the height to the resistance: 4 + 2 = 6 (meters).
The next step is to determine the m³ / hour, converting the power into the required heat: 10 m² of area \u003d 1 kW. But, if the walls of the building provide sufficient thermal insulation, 0.8 kW is taken into account, insufficient - 1.2 kW. Take for example a house of 200 m² with sufficiently warm and thick walls: 200/10 * 0.8 = 16 kW. We translate into other units of measurement: 16 * 0.86 \u003d 13.76 kcal.
Then you should decide on the desired temperature difference in the heating system. Experts recommend taking no more than 8-10 ° C, since higher rates can adversely affect the operation of the boiler. In addition, to obtain them, a sufficiently powerful unit is required, the operation of which will increase the consumption of electricity. Let's stop at the maximum option - 10 ° C. We get: 13.76 / 10 \u003d 1.37 m³ / hour.
To summarize: for a two-story building with good thermal insulation and a total area of 200 m², where the heating system uses bimetallic batteries, the circulation pump should have a capacity of 1.37 m³ / h at a pressure of 6 meters. Ideally, the unit should have such indicators at the second speed, it is desirable to choose the model itself with three speeds.
How to choose a booster pump for a heating system?
Equipment of this type is represented by fairly compact units, the installation of which is carried out directly on the pipe. Their main purpose is to normalize the pressure in the system. Pressure pumps are distinguished by their quiet operation, affordable cost, relatively simple installation and unpretentious maintenance. However, it must be understood that even the best booster unit will increase the pressure by a maximum of 1 atmosphere per point.
When choosing injection equipment, consider:
- minimum and maximum pressure in the existing heating network;
- estimated coolant consumption;
- desired pressure after installation of the unit.
Injection pumps are manual and automatic. The second type is more preferable due to the presence of a flow control sensor: when the system is turned on, the unit operates, and when it is out of operation, it turns off by itself. This greatly extends the life of the equipment.
How to choose a pump for heating a private house?
Learning about the principles of work and selection various kinds pumps for the heating system, many people have a question about which type of units to give preference to. The heating network may well be equipped with two types of pumping equipment at once - it all depends on its complexity. The circulation model will ensure the movement of water through the system, increasing its efficiency. The pressure pump will increase the pressure in some areas. Most often it is installed directly at the heating boiler.
However, the usual heating system of a private house can completely do without a booster unit. This type of pump is considered narrow-profile and is not used in simple heating systems. It will not work to replace the circulation pump with a pressure model - they have completely different tasks and the principle of operation. The first sets the coolant in motion by suction and ejection, acting due to centrifugal force. The second has an impact directly on the pressure, increasing it.
Therefore, in this case, the option "either one or the other" does not work. Specialists will be able to quickly determine whether a booster pump is needed in the heating system, or without it, the heating efficiency will be sufficient.
Now you know how to choose the right pump for the heating system, but we still recommend contacting professionals. Since only experienced craftsmen will be able to take into account all the features of the existing system and make the most correct decision!